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US20070260072A1 - Concurrent Sulfur Dioxide Oxidation Process and its Use in Manufacture of Tetrabromophthalic Anhydride - Google Patents

Concurrent Sulfur Dioxide Oxidation Process and its Use in Manufacture of Tetrabromophthalic Anhydride Download PDF

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Publication number
US20070260072A1
US20070260072A1 US11/568,308 US56830804A US2007260072A1 US 20070260072 A1 US20070260072 A1 US 20070260072A1 US 56830804 A US56830804 A US 56830804A US 2007260072 A1 US2007260072 A1 US 2007260072A1
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Prior art keywords
sulfur
catalyst
gaseous stream
bed
sulfur trioxide
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William Harrod
Tyson Hall
Christopher Knight
John Prindle
David Armstrong
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Albemarle Corp
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Albemarle Corp
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/69—Sulfur trioxide; Sulfuric acid
    • C01B17/74—Preparation
    • C01B17/76—Preparation by contact processes
    • C01B17/78—Preparation by contact processes characterised by the catalyst used
    • C01B17/79—Preparation by contact processes characterised by the catalyst used containing vanadium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/69—Sulfur trioxide; Sulfuric acid
    • C01B17/74—Preparation
    • C01B17/76—Preparation by contact processes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/54—Preparation of carboxylic acid anhydrides
    • C07C51/567—Preparation of carboxylic acid anhydrides by reactions not involving carboxylic acid anhydride groups

Definitions

  • This invention relates to improved process technology pertaining to oxidation of sulfur dioxide to sulfur trioxide, and to improving operations in which oxidation of sulfur dioxide to sulfur trioxide is involved.
  • the oxidation of sulfur dioxide to sulfur trioxide using oxygen or air and a suitable catalyst such as vanadium pentoxide is well known. Such an oxidation step is typically included in the contact process for producing sulfuric acid. Also, passing a gaseous stream containing sulfur dioxide, air and some sulfur trioxide through a bed of a vanadium-containing sulfuric acid catalyst such as preferably used in the practice of this invention maintained at about 824-1100° F. (ca. 440-593° C.) to oxidize sulfur dioxide to sulfur trioxide has been carried out heretofore. Further, it is known that sulfur can be oxidized into sulfur dioxide using a suitable oxidant such as air (auto ignition 261° C.) or oxygen (at less than 260° C.). However, the conversion of sulfur dioxide into sulfur trioxide requires a temperature activated catalyst such as a vanadium-containing catalyst, e.g., vanadium pentoxide or the like.
  • a temperature activated catalyst such as a vanadium-containing catalyst,
  • this invention provides an improved process in which a gaseous stream comprised of sulfur dioxide, sulfur trioxide, and oxygen and/or air is passed through and in contact with a bed of a vanadium-containing catalyst such as a vanadium oxide catalyst (typically vanadium pentoxide), and preferably a bed of a mixture of complex inorganic salts (oxosulfato vanadates) containing sodium, potassium and vanadium salts on crystalline silica support, or a catalyst including silica as a support within a salt mixture comprised of potassium and/or cesium sulfates, and vanadium sulfates coated on the solid silica support, that oxidizes sulfur dioxide to sulfur trioxide and that releases therefrom a product gaseous stream comprised of sulfur trioxide.
  • a vanadium-containing catalyst such as a vanadium oxide catalyst (typically vanadium pentoxide)
  • oxosulfato vanadates complex inorganic salts
  • the improvement comprises having molten sulfur come into contact with the catalyst and maintaining the catalyst bed at one or more temperatures at which (i) sulfur coming into contact with the catalyst is vaporized before the gaseous product(s) formed therefrom are released from a downstream end portion of the catalyst bed and (ii) the gaseous stream released from the downstream end of said bed has an enriched content of sulfur trioxide.
  • the temperatures of the catalyst bed bring about (i) and (ii) above differ from each other to some extent.
  • the vanadium-containing catalyst bed should be at one or more temperatures in the range of about 450 to about 700° C., and preferably in the range of about 450 to about 600° C.
  • one or more temperatures in the range of about 300 to about 450° C. are sufficient although one or more temperatures in the range of about 300 to about 700° C. can be used.
  • One of the features of the above embodiment of this invention when alternative a) is employed is that because of the high temperature(s) at which the catalyst bed is operated, the sulfur is vaporized as it comes into contact with the catalyst bed. This enables the vapors to be subjected to oxidation as they pass through the catalyst bed so that the gaseous stream released from the downstream end of catalyst bed has an enriched content of sulfur trioxide.
  • sulfur vaporizes to such an extent that unduly rapid formation and buildup of sulfur coatings or deposits on the catalyst surfaces does not occur. Thus the catalytic activity of the catalyst in the bed is not adversely affected.
  • Another embodiment of this invention is an improvement in a process in which a first gaseous stream comprised of sulfur dioxide, sulfur trioxide and oxygen and/or air is passed into a bed of a vanadium-containing catalyst that oxidizes sulfur dioxide to sulfur trioxide and that releases therefrom a product gaseous stream comprised of sulfur trioxide.
  • the improvement comprises oxidizing sulfur with air, oxygen and/or sulfur trioxide (preferably with a gaseous stream which contains (i) at least sulfur trioxide and air or oxygen, or (ii) sulfur trioxide, air and added oxygen) to form a second gaseous stream enriched in sulfur dioxide and introducing at least a portion of the second gaseous stream into the first gaseous stream to form a mixed gaseous stream, and passing the mixed gaseous stream into an upstream portion of the above catalyst bed maintained at one or more temperatures in the range of about 450 to about 700° C., and preferably in the range of about 450 to about 600° C. This results in the formation of a product stream emanating from a downstream portion of the catalyst bed that is enriched in sulfur trioxide.
  • the amount of sulfur trioxide in the product stream tends to be greater than could be predicted from the oxidation of the total amount of sulfur dioxide in the mixed gaseous stream.
  • the oxidation of sulfur in this embodiment of the invention is carried out in a separate reactor which feeds its effluent stream as a side stream into the first gaseous stream. This reactor is not an inline reactor.
  • the first gaseous stream need not contain sulfur trioxide if sulfur trioxide is used in the oxidation of the sulfur in such separate reactor and if an excess amount of sulfur trioxide is fed into the separate reactor so that the feed to the first gaseous stream from the separate reactor contains some residual sulfur trioxide.
  • the first gaseous stream and the feed to the first gaseous stream from the separate reactor both contain sulfur trioxide as this tends to further increase the amount of sulfur trioxide emanating from the vanadium-containing catalyst bed over and above that which could be predicted from the sum of (A) the amount of sulfur trioxide formed by direct mole-for-mole oxidation of sulfur dioxide to sulfur trioxide and (B) the total amount of sulfur trioxide present in the first gaseous stream and in the feed to the first gaseous stream from the separate reactor, assuming all such sulfur trioxide passed through the catalyst bed unchanged.
  • the catalyst used is preferably a fixed bed of a vanadium-containing catalyst that oxidizes sulfur dioxide to sulfur trioxide and that releases therefrom a product gaseous stream comprised of sulfur trioxide.
  • FIG. 1 is a schematic flow diagram of a preferred way pursuant to this invention of carrying out a process of producing SO 3 from a gaseous stream of SO 2 containing oxygen and/or air and a minor amount of SO 3 .
  • FIG. 2 is a schematic side view diagram of a reactor in which the sequential reactions of equations (1) and (2) above can be carried out.
  • FIG. 3 is a schematic flow diagram of a preferred way of utilizing a process of this invention in forming oleum and using the oleum as a reaction medium in the preparation of a commercially important flame retardant.
  • FIG. 4 is a schematic flow diagram of another way pursuant to this invention of carrying out a process of producing SO 3 from a gaseous stream of SO 2 containing oxygen and/or air and preferably a minor amount of SO 3 wherein a side stream comprised of system-generated sulfur dioxide is fed into a system such as that of FIG. 1 but without feeding sulfur into the system as in FIG. 1 .
  • FIG. 5 is a schematic flow diagram of laboratory apparatus used in developing information and data useful in scale up of process technology of this invention.
  • FIG. 5 the chief parts of the laboratory apparatus used to gather information and data, are identified by a different set of numerals.
  • vanadium-containing catalyst standing alone means a catalyst which may or may not be at least in part on a surface of a catalyst support and which catalyst in either such case (i) contains vanadium in one or more chemical forms which need not be metallic vanadium itself, (ii) when at one or more temperatures in the range of about 450 to about 700° C.
  • vaporized with reference to sulfur such as in terms such as “sulfur is vaporized” or “the vaporized sulfur” or the like does not mean that the vapors must be composed exclusively of elemental sulfur in vaporized form. Rather the vapors are composed of whatever is produced when molten sulfur approaches and/or contacts the hot surfaces of the vanadium-containing catalyst bed which is at one or more temperatures in the range of about 450 to about 700° C. in the presence of a gaseous flow comprised of sulfur dioxide, sulfur trioxide, and air, oxygen, or air enriched in oxygen.
  • vanadium-containing catalyst that oxidizes sulfur dioxide to sulfur trioxide does not mean that in the practice of this invention, the catalyst only serves the function of oxidizing sulfur dioxide to sulfur trioxide. Because of the complexity of the gaseous mixtures in contact with the catalyst, other reactions referred to in the body of this document may occur. Thus, the qualification that the catalyst “oxidizes sulfur dioxide to sulfur trioxide” is a descriptor to identify one function that the catalyst must be able to perform.
  • total moles of oxygen per total moles of sulfur refers to the molar ratio of (a) the total moles of elemental oxygen, oxygen in sulfur dioxide, and oxygen in sulfur trioxide to (b) the total moles of elemental sulfur, sulfur in sulfur dioxide, and sulfur in sulfur trioxide, wherein the components of (a) and of (b) are those present in the system being referred to.
  • the reactor in which the fixed bed of vanadium-containing catalyst is disposed (positioned) can be in any position relative to ground level.
  • a few non-limiting positions include for example horizontal, substantially horizontal, vertical, substantially vertical, upwardly inclined, downwardly inclined, and so on.
  • the reactor is in an upstanding (upright) position.
  • the reactor can have any shape and cross-sectional configuration that serves the purpose of enabling the process of this invention to be conducted therewith as described herein.
  • the reactor will need a gas inlet portion and a gas outlet portion and should be configured such that all or substantially all of the incoming gaseous stream will pass through the fixed bed catalyst that is maintained therein.
  • the reactor needs to be equipped with heating apparatus that will enable the catalyst to be heated (e.g., to one or more temperatures in the range of about 450 to about 700° C., and preferably in the range of about 450 to about 600° C.) during startup in order to cause the process to be initiated.
  • the process is sufficiently exothermic as not to require addition of further heat during the course of the reaction as temperature control can be maintained by adjusting the feed rates to the reactor.
  • the catalyst bed is kept at one or more temperatures in the range of about 450 to about 700° C., brief excursions outside of this range can usually br tolerated if the period of the excursion is sufficiently brief.
  • the reactor Since the reactor is continuously exposed to internal high temperature conditions during operation and since corrosive gases are being handled and produced within the reactor, it should be fabricated from suitable corrosive resistant materials.
  • Alonized stainless steel reactors and reactors constructed of high nickel-content alloys serve as non-limiting examples of reactors made with suitable materials of construction. Two or more reactors may be used in tandem, if desired. Indeed, it is feasible to have multiple catalyst beds arranged in series with sulfur and oxygen or air feeds between each of them in order to moderate the exothermic nature of the oxidation reaction.
  • vanadium-containing catalysts can be used in the practice of this invention provided that the catalyst has the ability to oxidize sulfur dioxide to sulfur trioxide.
  • modified vanadium pentoxide catalysts such as described in U.S. Pat. Nos. 3,793,230 and 4,285,927 may be used.
  • a vanadium pentoxide catalyst can be on a suitable support so that structural integrity is maintained and so that the catalyst can otherwise withstand the high temperature(s) at which the bed is operated.
  • suitable supports include high temperature resistant ceramics, alumina, silica, silica alumina, zeolites, and similar materials.
  • vanadium-containing catalysts used in the practice of this invention, are sulfuric acid catalysts such as are available from Monsanto Enviro-Chem as LP-120, LP-110, LP-220, T-210, T-516, T-11, Cs-120, Cs- 110, Cs-210, and presumably LP-1150. According to a product brochure by Monsanto Enviro-Chem concerning such sulfuric acid catalysts and obtained from their website on Apr. 13, 2004, the LP-120, LP-110, LP-220, Cs-120, and Cs-110 are available in the shape of rings, whereas T-210, T-516, T-11, and Cs-220 are available in the shape of pellets.
  • the main components of these catalysts include SiO 2 (silica as a support), vanadium (V), potassium (K), and/or cesium (Cs), and various other additives. It appears from this brochure that these catalysts may be formed from a molten salt mixture of potassium/cesium sulfates and vanadium sulfates, coated on a solid silica support. Monsanto Enviro-Chem further states that because of the unique chemistry of this molten salt system, vanadium is present as a complex sulfated salt mixture and “NOT” as vanadium pentoxide (V 2 O 5 ).
  • the brochure further states that the catalyst is more correctly called a “vanadium-containing” catalyst rather than the commonly-used “vanadium pentoxide” catalyst. It further appears from these brochures that LP-120, T-210, LP-110, and T-11 catalysts are potassium promoted, whereas Cs-120, Cs-110, and Cs-210 are cesium promoted. The cesium promoted catalysts are indicated to be more expensive, but capable of operation in a catalyst bed at lower temperatures in the range of 390-410° C.
  • the residence time of the gases within the catalyst bed should be sufficient to enable high conversions to sulfur trioxide, and thus limited residence times (up to 5-10 seconds) are generally sufficient.
  • One of the preferred embodiments of this invention is to utilize a fixed bed of a vanadium-containing catalyst to oxidize sulfur dioxide into sulfur trioxide in an upstanding reactor (upright, in other words the reactor need not be perfectly vertical as it can lean or be tilted somewhat) with the incoming gaseous stream comprised of sulfur dioxide and oxygen and/or air (which stream preferably also contains sulfur trioxide) entering into the upper portion of the reactor into a headspace above the catalyst bed, and to introduce the molten sulfur above the upper end portion of the catalyst, preferably above or in an upper end portion of the headspace.
  • the molten sulfur travels substantially downwardly toward the upper end portion of the catalyst bed and at least a portion if not substantially all of the sulfur is vaporized as it contacts and/or comes into close contact with the hot upper end portion of the catalyst.
  • the provision of the headspace above the catalyst bed provides a zone in which at least some of the vapors produced by the vaporization of the sulfur and at least some of the incoming gaseous stream can come into contact with each other and be carried by the force of the incoming gaseous stream into the catalyst bed. Without desiring to be bound by theory, one may speculate that some oxidation of sulfur vapors may even be initiated in the lower regions of the headspace.
  • the amount of sulfur trioxide released or emerging from the downstream end portion of the catalyst bed is higher than the amount of sulfur trioxide that would be released or that would emerge from the same downstream end portion of the same catalyst bed under the same operating conditions and with the same incoming gaseous stream in the absence of the sulfur addition.
  • Such increased amount of sulfur trioxide released or emerging from the downstream end portion of the catalyst bed is apparently due to the occurrence of at least two reactions in the process when the incoming gaseous feed stream contains sulfur trioxide as well as sulfur dioxide and air and/or oxygen.
  • each mole of SO 3 being fed through the oxidation catalyst is unchanged and provides one mole of SO 3 in the product released or emanating from the downstream end portion of the catalyst.
  • each mole of SO 3 upstream from the catalyst is converted in a two-step reaction sequence into 1.5 moles of SO 3 in the product emanating from the catalyst.
  • reaction of equation (1) which can be considered as oxidation of sulfur to SO 2 apparently takes place first at least to some extent, and then both the original SO 2 and the newly-formed SO 2 are catalytically oxidized via equation (2) to form SO 3 whereby an increase in total SO 3 formation occurs as compared to the same operation with the same quantities of materials except that no sulfur is fed.
  • it is preferred to conduct these reactions in a simple reactor such as schematically depicted in FIG. 3 of the drawings.
  • both the oxidation of sulfur into SO 2 and subsequent catalytic oxidation of SO 2 into SO 3 can occur at least in part in a single two-stage reactor or reaction zone in which there is a headspace above or a “dead” space ahead of the catalyst bed.
  • the preferred embodiments of this invention described in this paragraph involve a dichotomy in that while it is desired to produce sulfur trioxide from sulfur dioxide, the process of such preferred embodiments first actually appears to reduce the amount of sulfur trioxide originally present in the incoming gaseous stream by converting that sulfur trioxide to sulfur dioxide followed by the oxidation of at least a portion of that newly-formed sulfur dioxide into sulfur trioxide.
  • a vanadium-containing sulfuric acid catalyst such as a vanadium-containing catalyst such as vanadium pentoxide, and preferably a bed of a mixture of complex inorganic salts (oxosulfato vanadates) containing sodium, potassium and vanadium salts on crystalline silica support, or a catalyst including silica as a support within a salt mixture comprised of potassium and/or cesium sulfates, and vanadium sulfates coated on the solid silica support, that oxidizes sulfur dioxide to sulfur trioxide and that releases therefrom a product gaseous stream comprised of sulfur trioxide.
  • a vanadium-containing sulfuric acid catalyst such as a vanadium-containing catalyst such as vanadium pentoxide
  • oxosulfato vanadates complex inorganic salts
  • the improvement comprises oxidizing sulfur with air, oxygen and/or sulfur trioxide (preferably with a gaseous stream which contains (i) at least sulfur trioxide and air or oxygen, or (ii) sulfur trioxide, air and added oxygen) to form a second gaseous stream enriched in sulfur dioxide and introducing at least a portion of the second gaseous stream into the first gaseous stream to form a mixed gaseous stream, and passing the mixed gaseous stream into an upstream portion of the above catalyst bed maintained at one or more temperatures in the range of about 450 to about 700° C., and preferably in the range of about 450 to about 600° C. This results in the formation a product stream emanating from a downstream portion of the catalyst bed that is enriched in sulfur trioxide.
  • the amount of sulfur trioxide in the product stream tends to be greater than could be predicted from the oxidation of the total amount of sulfur dioxide in the mixed gaseous stream to sulfur trioxide.
  • the oxidation of sulfur in this embodiment of the invention is usually carried out in a separate reactor.
  • a gaseous SO 2 feed at 10 which optionally contains some SO 3
  • a recycled gaseous stream containing oxygen and/or oxygen-depleted air (mainly nitrogen) and, optionally (but preferably), a minor amount of SO 3 at 12 are mixed with fresh air or oxygen from 14 and the resultant gaseous mixture is drawn into blower 15 .
  • Blower 15 propels the resultant mixture through indirect heat exchanger 20 which in part heats this gaseous mixture.
  • molten sulfur from 16 whereby when SO 3 is present in the recycled gaseous stream at 12 , additional SO 2 is deemed to be formed by reaction of sulfur with SO 3 .
  • the resultant enriched SO 2 stream is then passed into reactor 25 containing a suitable vanadium-containing catalyst (most preferably a fixed bed of supported vanadium-containing catalyst) for oxidizing SO 2 to SO 3 .
  • a suitable vanadium-containing catalyst most preferably a fixed bed of supported vanadium-containing catalyst
  • This gaseous product mixture enriched in SO 3 is passed from reactor 25 as at 27 and through heat exchanger 20 wherein heat from the exothermic reaction in reactor 25 is employed to heat the mixture coming from blower 15 , and thereby reduce the temperature of the gaseous mixture coming from reactor 25 .
  • This latter mixture is then further cooled in cooler 30 and then passed into distillation column 35 .
  • the distillation column is operated so as to remove the more volatile components of the mixture as the overhead which thus constitutes the recycled gaseous stream referred to at the outset.
  • the desired SO 3 is taken from the bottom of column 35 as at 37 .
  • the makeup of the recycled gaseous stream will vary somewhat depending on whether air, oxygen, or air enriched with oxygen is fed to the gaseous mixture upstream from the place where the sulfur from 16 is introduced. If pure oxygen is fed, the recycled gaseous stream will contain unreacted gases and in preferred embodiments, will also contain some SO 3 . If air or air enriched with oxygen is used, the recycled gaseous stream will contain nitrogen as well as other unreacted gases and in preferred embodiments, will also contain some SO 3 . In either case where SO 3 is present, the proportion of SO 3 in the recycled gaseous stream typically will be less than about 10 percent by volume.
  • the ratios of SO 2 to SO 3 can also vary. Typically this ratio on a molar basis will be in the range of about 15:1 to about 25:1, and preferably in the range of about 22:1 to about 24:1.
  • the amount of sulfur fed from 16 should be at least about 0.002 mole per mole of SO 2 in the gaseous mixture to which the sulfur is added, and typically will be in the range of approximately 0.005 to 0.020 mole, and preferably in the range of approximately 0.015 to 0.018 mole, of sulfur per mole of SO 2 in such gaseous mixture. Greater amounts of sulfur can be used, but ordinarily will serve no useful purpose.
  • this gaseous stream will contain in the range of approximately 1.25 to 1.75 moles of molecular oxygen per mole of sulfur as SO 2 and elemental sulfur present in such stream.
  • reactors having higher operating temperature limits more than about 2.0 moles of molecular oxygen per mole of sulfur as SO 2 and elemental sulfur can be present in the gaseous stream entering the catalyst bed.
  • the flow rates of oxygen, SO 2 -SO 3 gaseous mixture (or SO 2 when an SO 2 -SO 3 gaseous mixture is employed), and sulfur are measured and monitored using flowmeters.
  • the amount of SO 3 is calculated based upon the distillation temperature relative to the mole fraction SO 3 at a specific distillate temperature.
  • Molten sulfur can be introduced to the gaseous mixture in different ways.
  • the gaseous mixture can be passed under pressure through the molten sulfur or the molten sulfur can be sprayed into the gaseous mixture.
  • the molten sulfur is initially conveyed by pumping the molten sulfur into downwardly flowing gaseous stream approaching the reactor so that both the force of the stream and gravity cause the sulfur to proceed downwardly toward and/or onto the upper end portion of the catalyst bed where the sulfur is vaporized.
  • the molten sulfur will almost instantaneously react with SO 3 in the incoming stream to form, in situ, additional SO 2 , and thus at that point reduce or eliminate the SO 3 content in the stream.
  • temperatures used in the process can vary depending upon the particular equipment used and the rates and volumes at which the materials are being processed provided of course that the sulfur fed to the gaseous stream is fully vaporized.
  • the temperatures of the zone in which the molten sulfur reacts with the SO 3 in the incoming stream are typically within the range of about 232 to about 600° C. and preferably in the range of about 450 to about 600° C. for incoming gaseous feeds in the range of about 2500 to about 10,000 kg/hour, provided the equipment can be safely operated under these conditions.
  • the temperatures in the oxidation catalyst zone are typically in the range of about 450 to about 700° C. and preferably are in the range of about 450 to about 600° C.
  • the temperature(s) in the catalyst bed should not reach the temperature at which the unsupported catalyst melts or loses its ability to perform its role as a catalyst or at which the supported catalyst melts, loses its ability to perform its role as a catalyst, undergoes material degradation or suffers loss of structural integrity. Departures from the foregoing ranges are permissible and are within the scope of this invention provided that the departures do not materially interfere with the process and do not constitute hazardous operating conditions in relation to the processing equipment being used.
  • Operating pressures of at least 10 psig, and preferably at least 100 psig are preferred for converting SO 2 to SO 3 .
  • Maximum pressures are preferably about 150 psig, but can be higher if desired.
  • reactor 25 comprises mixing sections in which vaporized sulfur reacts with SO 3 to enrich, in situ, the SO 2 concentration, and a catalytic section in which the oxidation of SO 2 to SO 3 takes place.
  • FIG. 2 schematically depicts a reactor generally referred to as 25 A as a preferred configuration for such reactor 25 .
  • Reactor 25 A itself comprises housing 50 containing a fixed catalyst bed 55 having a headspace or dead volume 60 (an unoccupied zone) above the top of the bed.
  • headspace or dead volume 60 an unoccupied zone
  • at least a portion of bed 55 is maintained at one or more suitable operating temperatures in the range of about 450 to about 700° C. and preferably in the range of about 450 to about 600° C. so that oxidations such as result in the formation of additional sulfur trioxide take place therein.
  • conduit 65 Leading to dead volume 60 is conduit 65 into which is forced molten sulfur from 16 so that the molten sulfur is transported downwardly both by gas flow and gravity through an entry port in the top of reactor 25 A and all or at least a portion thereof impinges upon the top of the hot catalyst bed. Note that some or possibly most if not all of the sulfur may possibly vaporize before reaching the catalyst bed. On approaching and/or impinging upon the catalyst bed the molten sulfur is vaporized and the sulfur vapors mix with the incoming gases in headspace or dead volume 60 and are swept by the incoming gases into the catalyst bed where all or substantially all SO 2 is oxidized to SO 3 utilizing oxygen from air and/or oxygen fed upstream as at 14 . A gaseous product stream enriched in SO 3 is taken from reactor 25 A via conduit 27 .
  • the approximate heat-limited flowrates around reactor 25 are 20,000 lb/hr (9072 kg/hr) of SO 2 /SO 3 gaseous mixture containing in the range of about 0.010 to about 0.042 mole of SO 3 per mole of SO 2 , 175 lb/hr (79 kg/hr) of sulfur, and 560 lb/hr (254 kg/hr) of oxygen.
  • reactor 25 A having a total height of about 10 feet, and a diameter of 3 feet with a 4-foot high headspace or dead volume 60 and a 6-foot high catalyst bed packed with supported vanadium-containing catalyst having an average particle size of about 0.25-0.50 inch, has been found very suitable.
  • Reactor 25 A is preferably constructed of alonized stainless steel.
  • the reactor is heated by an indirect gas-fired furnace and the temperature is easily maintained from the resulting exotherms of the oxidation reactions.
  • Distillation column 35 is used to separate the recycle mixture of SO 2 /SO 3 and inerts from the product SO 3 . As with the reactor, it is preferred to run the column under 100 psig although higher pressures can be used, within normal high-pressure equipment limitations.
  • the flow diagram of FIG. 1 can be modified without departing from the scope of this invention.
  • the incoming gaseous stream approaching the sulfur feed at 16 can be devoid of SO 3 .
  • the oxygen and/or air feed from 14 can occur at other locations such as downstream from the blower 15 , or to the gaseous effluent from distillation column 35 . It is desirable however that the addition of the oxygen and/or air occur upstream from the feed of the molten sulfur. Also, higher ratios of SO 3 :SO 2 are possible in the inlet of the reactor.
  • Molten sulfur can be added to a horizontally disposed reactor 25 provided the sulfur is carried by the gaseous stream into the hot catalyst bed or that the sulfur drops onto the front portion of the hot catalyst bed and is vaporized thereby and swept into the rest of the catalyst bed.
  • Another variant of the invention is to cause the molten sulfur to impinge upon a hot high temperature resistant inert ceramic or inert metal surface disposed (positioned) at a suitable location ahead of the catalyst bed so that the sulfur is vaporized in the incoming gaseous stream and is carried into the catalyst bed.
  • FIG. 3 there is schematically depicted therein a process flow diagram of a preferred embodiment of this invention, namely utilization of the above-described SO 3 generation process for use in the production of another product such as a brominated flame retardant.
  • SO 3 eluent from the distillation is directly used to achieve electrophilic aromatic bromination using a highly deactivated substrate (reactant A) of structure which prohibits toward the use of common Lewis acid catalysts, such as AlCl 3 , AlBr 3 , FeCl 3 , FeBr 3 , etc., for this reaction.
  • reactant A highly deactivated substrate
  • reactants A e.g., phthalic anhydride
  • B e.g., bromine
  • an activating solvent namely a concentrated oleum.
  • This concentrated oleum typically 25-65% SO 3 by weight, is generated by passing SO 3 formed as described above, for example in connection with FIG. 1 , and taken from the bottom of column 35 via line 37 into tower 75 .
  • the SO 3 is mixed with depleted oleum (e.g., 22% oleum) coming from reactor 70 via line 73 so that in tower 75 a more concentrated oleum (e.g., 65% oleum) is regenerated and delivered from the bottom of tower 75 into reactor 70 as indicated via line 77 .
  • Any SO 2 and SO 3 emanating from reactor 70 are recycled as indicated via line 80 to the system such as schematically depicted in both FIGS. 1 and 3 (except that the stream in line 80 in FIG. 3 corresponds to the feed in line 10 in FIG.
  • the solid product is recovered as at 78 and processed downstream therefrom for packaging.
  • FIG. 4 depicts another way pursuant to this invention of carrying out a process of producing SO 3 from a gaseous stream of SO 2 containing oxygen and/or air and a minor amount of SO 3 .
  • FIG. 4 is the same as FIG. 1 as described above except that reactor 90 is provided, and that the molten sulfur feed at 16 of FIG. 1 is omitted (but could be included if desired).
  • Fed into reactor 90 are molten sulfur as at 92 , and an oxidant as at 94 .
  • the oxidant can be sulfur trioxide or air and/or oxygen, or it can be any combination of these.
  • the oxidant preferably is or includes sulfur trioxide.
  • the oxidants When two or all three of air, oxygen, and sulfur trioxide are used as the oxidants they can be fed separately or as one or more preformed mixtures of gaseous oxidants. Alternatively, the sulfur is melted after being charged and then one or more feeds of the gaseous oxidant(s) employed are initiated, such that a gaseous stream enriched in sulfur dioxide is propelled out of reactor 90 and into the gaseous stream as at 95 to form a mixed stream which is carried into the catalyst bed in reactor 25 . It will be appreciated that the oxidations in reactor 90 are uncatalyzed oxidation reactions. When sufficient air or oxygen to conduct the oxidation(s) occurring in reactor 25 is introduced by the stream as at 95 , the feed at 14 may be omitted, if desired. Otherwise the operation depicted in FIG. 4 is as described above in connection with FIG. 1 . Note that the gaseous feed as at 95 can be at any suitable location upstream from reactor 25 .
  • a 1-inch by 24-inch quartz furnace tube was filled with 1 ⁇ 4-inch ceramic Berl saddles containing 2.02 g of sulfur (preloaded). The materials were placed inside a furnace operated at 450° C. and the exit vent was fitted with a trap containing 18 g of NaOH as an 11.7 wt % aqueous solution in a gas absorption bottle. Sulfuric acid (106.35 g) was pumped into the furnace tube during a period of about 2.5 hours with observation of steam reflux which included traces of vaporized sulfur. The exit gas was trapped as sodium sulfite (Na 2 SO 3 ) and analyzed using excess iodine and then back-titrated with sodium thiosulfate. The SO 2 yield was 49.33%.
  • Example 1 The procedure of Example 1 was repeated using 2.16 g of sulfur (preloaded) and 24.72 g of 96% H 2 SO 4 , which were placed inside the furnace (operated at 450° C.) and the exit vent was fitted with a trap comprised of a 250 mL gas absorption bottle containing 152.05 g of 21.1 wt % aqueous NaOH. Sulfuric acid was pumped into the furnace tube for a period of about 0.3 hour with observation of steam reflux which included traces of vaporized sulfur. The exit gas was trapped with sodium sulfite (Na 2 SO 3 ) and analyzed using excess iodine and then back-titrated with sodium thiosulfate. The SO 2 yield was 50.8%.
  • Example 1 The procedure of Example 1 was repeated except that 4.5 g, 140 mmols of sulfur were preloaded into the furnace tube and reacted with 81 mL (149.04 g, 1.52 mols) of H 2 SO 4 in a 1-inch by 18-inch pipe heated to 452-464° C. inside a furnace. The exit gas was trapped using aqueous NaOH and analyzed as in Example 1. The total SO 2 yield was 86%.
  • the following numerals represent the following parts 100 is a tube furnace, 102 is an SO 3 heat tube, line 104 is a nitrogen feed, 106 is molten sulfur, 108 is a heating mantle, 110 is a sulfur temperature gauge, 112 is an overhead temperature gauge, and 114 is a vent line to an empty flask and scrubbers, 116 is telfon tubing, 118 is a sulfur trioxide feed tank, 120 is a feed tank pressure gauge, 122 is a nitrogen feed for tank pressurization, 124 is a nitrogen feed for post experiment flushing of the system, and 126 is an SO 3 balance. It will be noted from FIG.
  • the exit gases were passed through an empty flask to knock-out any entrained liquids and then were collected in a series of two scrubbers.
  • the first scrubber contained water (800 gms) and the second scrubber contained a 25 wt % caustic solution (840 gms).
  • the caustic scrubber was maintained at 40° C. to prevent Na 2 SO 3 precipitation and pluggage of the dip-tube. Accurate analysis of the scrubber contents for SO 2 and SO 3 was difficult with this approach.
  • the materials in these scrubbers were changed to improve the analysis.
  • the first scrubber contained a bromine/water mixture (25 Ogms/380.2 gms) while the second scrubber contained only water (800 gms).
  • the first scrubber oxidized the SO 2 to SO 3 by the following reaction: SO 2 +2H 2 O+Br 2 ⁇ H 2 SO 4 +2HBr
  • the second scrubber trapped the SO 3 and HBr exiting from the first scrubber.
  • Samples of each scrubber were collected and analyzed for wt % bromide and wt % acid. During each experimental run, the unit was operated for 35-60 minutes. Conditions spanning a wide range of sulfur:SO 3 molar ratios (2.4:1 to 0.25:1) were investigated.
  • Table 1 contains a summary of the results from these four sulfur oxidation experimental runs.
  • the amount of sulfur conveyed with nitrogen was calculated with ChemCad by assuming the nitrogen was saturated with sulfur vapors at the molten sulfur conditions. Note that the molten sulfur was held at 365-390° C. for the excess sulfur experiments (runs 1 and 2) and at 290° C. for the excess SO 3 experiments (runs 3 and 4).
  • the SO 3 flowrate was varied from 1.0 to 1.8 gms/min. Even though equipment problems existed with all but one of the four experimental runs conducted, the results indicate that a substantial amount of the SO 3 and sulfur react to form SO 2 under suitable reaction conditions.
  • sulfur 267.5 gms
  • Air was fed continuously to the bottom of the tube through a quartz dip-tube.
  • the furnace temperature was maintained at 380° C. Both oxidation and vaporization of the sulfur occurred.
  • the vaporized sulfur was condensed and collected in a round-bottom flask.
  • the SO 3 produced from oxidation was trapped in a large scrubber.
  • the exit gas temperature was monitored throughout the oxidation process. Over the 6-8 hr period during this experimental run, the exit gas temperature fluctuated between 270 and 340° C. The majority of the residue was produced after the molten sulfur level in the tube fell below the dip-tube exit where the air was being fed.
  • a separate sample of commercial plant sulfur was submitted to an outside laboratory (Galbraith Laboratories, Inc.) to determine the carbon content.
  • the commercial plant sulfur was determined to contain 0.19 ⁇ 0.01 wt % carbon.
  • amorphous carbon powder (5 gms) was placed in a furnace tube with approximately 3-4 inches of glass beads on top to prevent powder entrainment.
  • Sulfur trioxide (approximately 80 gms) was fed over a 1.5-hour period through the carbon bed with the furnace temperature set at 538° C. (1000° F.). Following this feed period, the tube was allowed to cool and then was weighed to determine the carbon remaining.
  • Example 4-6 The results obtained in Examples 4-6 indicate that sulfur trioxide (SO 3 ) will oxidize sulfur to form sulfur dioxide (SO 2 ) at suitable operating temperatures used in the oxidation of SO 2 to SO 3 .
  • Conversion of sulfur in a 2-3 second residence time gas phase in a plug-flow reactor at 700° F. (ca. 370° C.) should be at least 90% or greater.
  • Small amounts of the reaction intermediate S 2 O 3 was observed to exit the reactor at shorter residence times.
  • Sufficient residue was collected from oxidation and vaporization of the commercial plant sulfur to perform an elemental analysis. This residue was primarily comprised of un-oxidized sulfur and elements contained in the quartz tube used during the test.
  • the commercial plant sulfur was analyzed for carbon content and determined to be 0.19 ⁇ 0.01 wt %.
  • the additional experiment of Example 6 suggests that carbon oxidation will occur at 700-1100° F. (ca. 370-593° C.) operating temperatures often used in the oxidation of SO 2 to SO 3 . Carbon oxid
  • this invention in its broadest aspects involves providing a catalyst zone which can be in a single reactor or in two or more reactors in series.
  • One or more vanadium-containing catalysts beds are in the reactor(s), preferably as one or more fixed beds. Different vanadium-containing catalysts can be used in the vanadium-containing catalyst bed(s).
  • At least one bed, and preferably all of the beds, in the catalyst zone contain a vanadium-containing catalyst that oxidizes sulfur dioxide to sulfur trioxide.
  • a first gaseous stream comprised of sulfur dioxide, sulfur trioxide, and air or oxygen or air mixed with additional oxygen. (Air mixed with additional oxygen is also known as air enriched with oxygen).
  • Emanating from the bed (or a last bed in a series of beds) is a second gaseous stream enriched in sulfur trioxide.
  • a feature of one such process is that sulfur, preferably molten sulfur, is introduced into at least the first gaseous stream so that the sulfur is vaporized and carried into the catalyst bed of the reactor (or a first catalyst bed in a series of catalyst beds) so that the stream emanating from the first catalyst bed (or from the first catalyst bed in a series of catalyst beds) is enriched in sulfur trioxide.
  • sulfur preferably molten sulfur
  • the stream emanating therefrom is the above second gaseous stream.
  • the stream emanating from the last catalyst bed in the series is the above second gaseous stream.
  • sulfur can be fed upstream from each catalyst bed so that vaporized sulfur is formed from the sulfur of each sulfur feed and such vaporized sulfur enters its downstream catalyst bed.
  • additional sulfur trioxide, and/or air or oxygen or air mixed with additional oxygen is also fed upstream from each catalyst bed.
  • heat removal from the stream emanating from each successive bed should be carried out because of the highly exothermic reactions taking place in the reactors.
  • a feature of another such process is that sulfur dioxide is generated from sulfur and sulfur trioxide, and/or air, oxygen, or air mixed with additional oxygen and the resultant sulfur dioxide-containing gaseous stream is added to the first gaseous stream referred to above.
  • this process embodiment is generally similar to the system described in the immediately preceding paragraph except that sulfur itself is not introduced into the first gaseous stream referred to above.
  • the make up of the feed(s) to the catalyst bed is/are preferably adjusted or controlled (or the feeds to the catalyst beds are preferably adjusted or controlled), and the amount(s) of sulfur and any additional air or oxygen or air mixed with additional oxygen added to the stream heading to the catalyst bed is/are preferably adjusted or controlled (or the feeds to the catalyst beds are preferably adjusted or controlled) to the numerical values given hereinabove so that significant increases in sulfur trioxide content in the final product stream are achieved.

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US20100284899A1 (en) * 2009-05-11 2010-11-11 Dieter Kita Generation of sulfur trioxide and sulfuric acid
US8679447B2 (en) 2011-01-11 2014-03-25 Albemarle Corporation Process for producing sulfur dioxide and sulfur trioxide

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US8107080B2 (en) * 2009-05-11 2012-01-31 Thermo Fisher Scientific Inc. Environmental control of fluid samples, calibration, and detection of concentration levels
CN102067954A (zh) * 2010-11-22 2011-05-25 杨开伦 一种利用电子受体物质使绒山羊增重增绒的方法
RU2526616C2 (ru) * 2013-03-21 2014-08-27 Александр Михайлович Андриевский Способ получения тетрабромфталевого ангидрида
KR102686164B1 (ko) * 2023-06-21 2024-07-22 주식회사 강원에너지 망초로부터 수산화나트륨 및 황산의 제조방법

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US20100284899A1 (en) * 2009-05-11 2010-11-11 Dieter Kita Generation of sulfur trioxide and sulfuric acid
WO2010132180A1 (fr) * 2009-05-11 2010-11-18 Thermo Fisher Scientific Inc. Génération du trioxyde de soufre et de l'acide sulfurique
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US8679447B2 (en) 2011-01-11 2014-03-25 Albemarle Corporation Process for producing sulfur dioxide and sulfur trioxide

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